A hole referred to so-called an ID hole is provided in a casing of a video tape cassette and the like. The hole is used to prevent erroneous erasure of data recorded on a magnetic tape or to identify a recorded format, a material of a magnetic substance of a tape and the like.
For example, as shown in an example of a relevant part of a high band 8 mm video tape cassette of FIGS. 1A and 1B, an erroneous erasure prevention member 103 capable of sliding in the longitudinal direction on the side surface 100a is provided at a position adjacent to a corner inside a casing of a cassette 100 formed by combining top and bottom shells (not shown in the figures) and an erroneous erasure prevention hole 101 functioning as the ID hole provided on the bottom surface of the cassette casing is opened and closed by moving the erroneous erasure prevention member 103.
An example of the erroneous erasure prevention member 103 has such a structure as a stepped shape formed of a plurality of bending portions as shown in FIG. 2, for example, and includes a lug portion 103a used for the moving operation, a half-disc shaped protruding portion 103b which opens and closes the erroneous erasure prevention hole 101 and an identification display portion 103c to recognize visually through an display window 102 opened in the side surface 100a of the cassette casing.
As shown in FIG. 1A, the erroneous erasure prevention member 103 is moved by laying a finger or the like on the lug portion 103a projecting from the inside of the display window 102 on the side surface 10a of the cassette casing so that the display portion 103c becomes visible in the whole display window 102. At this time, the protruding portion 103b of the erroneous erasure prevention member 103 closes the erroneous erasure prevention hole 101 to become a closed state. A position of the erroneous erasure prevention member 103 at this time is the position where the cassette is in a recordable state (REC position).
Next, as shown in FIG. 1B, the erroneous erasure prevention member 103 is moved by laying a nail on the lug portion 103a projecting from the inside of the display window 102 in the side surface 100a of the cassette casing so that the display portion 103c disappears from the display window 102 and a recording prohibition display panel 102a disposed behind becomes visible. At this time, the protruding portion 103b of the erroneous erasure prevention member 103, which has closed the erroneous erasure prevention hole 101, moves so that the erroneous erasure prevention hole 101 becomes an open state. A position of the erroneous erasure prevention member 103 at this time is the position where the cassette is in an non-recordable state (SAVE position).
Specifically, a detection hole is made to be the closed state at the recordable position and the detection hole is made to be the open state at the non-recordable position; that is, in a casing of a VHS video cassette or the like, for example, a nail has conventionally been provided for this hole when it is in a state of a blank cassette having nothing recorded yet and after recording, the nail is removed so that an existing record can not be deleted thereafter by erroneously making a duplicated recording; and hereupon this nail is made to be a movable one using the above described erroneous erasure prevention member, so that a state of nail-broken or nail-unbroken can be changed according to a necessity.
Further, though a mechanical switch is conventionally used in order to detect the state of nail-broken or nail-unbroken, it is also possible to use a photo-sensor or the like for the detection by irradiating light from below, and also it can be considered to have a construction in which the detection hole is made to be a through hole which pierces from the top surface to the bottom surface of the cassette and light is applied from one side of the through hole to be sensed on the other side thereof.
Conventionally, when magnetic recording of a different kind of format is performed on a cassette having the same shape in a recording and reproducing apparatus such as a VTR (Video Tape Recorder) for example, it is necessary to have detecting switches for identifying the format and for preventing the erroneous erasure. Conventionally, holes for the purpose of the ID hole as described above are provided according to a required number in a casing of a cassette when a format is decided, and those are judged by detecting an open or closed state of the ID holes using the detecting switches in a drive unit of the VTR provided at positions corresponding to those ID holes.
For example, a high band 8 mm video has an erroneous erasure prevention detecting switch of a cassette. FIG. 3A schematically shows an erroneous erasure prevention hole and an erroneous erasure prevention detecting switch of a high band 8 mm video tape cassette. The erroneous erasure prevention of the cassette is identified using an erroneous erasure prevention detecting switch 107, and the erroneous erasure prevention hole 101 becomes an open or closed state depending on a position of the erroneous erasure prevention member 103 which is visible from the display window 102, and thereby, it is judged whether the cassette is in a recordable state or in a non-recordable state. Moreover, in a 8 mm video, a detection hole not shown in the figure is provided for identifying either a normal 8 mm video tape cassette or a high band 8 mm video tape cassette, so that it is judged whether it is a normal one or a high band one.
On the other hand, when a higher format cassette which has been used for NTSC as a television broadcasting method, for example, is used in a new (higher) format such as, for example, a high vision, it becomes impossible to perform recording and/or reproduction in a conventional VTR due to a magnetic head and a signal processing circuit, since a magnetic tape which is a recording medium is made to be one having higher performance to record greater amount of data. For this reason, it is necessary to make the new format cassette not to be capable of recording in a conventional VTR. Following two methods can be considered for the purpose.
1. A Method of Changing a Cassette Size
A new product model is made to be capable of loading a new (higher) format only, or otherwise, it is necessary to have a complicated mechanism of higher/existing format compatible.
2. A method of Adding Another Detection Hole used for a Detecting Switch
It is necessary to keep an erroneous erasure prevention detecting switch for an existing format always turned off in a cassette for a higher format so that recording can not be performed with the existing format. Therefore, it becomes necessary to add two detection holes for detecting switches both for the purpose of identifying the higher/existing format and for the purpose of detecting the erroneous erasure prevention of the higher format cassette.
When a higher format supporting cassette shown in FIG. 4A is used, the erroneous erasure prevention hole 101 of an existing format supporting cassette is continuously kept in the open state and the erroneous erasure prevention detecting switch 107 of the existing format is turned off to prevent the erroneous erasure with the existing format.
When a higher cassette 110 is loaded into a VTR 120, a higher/existing format identification switch 122 is engaged with a higher/existing format identification hole 112 to be turned off as shown in FIG. 4A. Then, it is judged that the cassette is the higher cassette, and also, a higher format erroneous erasure prevention detecting switch 123 is turned on by an erroneous erasure prevention member 115 to become a recordable state.
Further, when the erroneous erasure prevention member 115 is moved to make a hole 113 for erroneous erasure prevention of the higher format become the open state, the higher format erroneous erasure prevention detecting switch 123 is turned off to become a non-recordable state as shown in FIG. 4B.
On the other hand, when an existing format supporting cassette shown in FIG. 5A is loaded, since there is no erroneous erasure prevention hole of higher format, the higher format erroneous erasure prevention detecting switch 123 is always turned on due to being depressed by a casing of a cassette 130 to prevent the erroneous erasure with the higher format.
When the existing cassette 130 is loaded into the VTR 120, the higher/existing format identification switch 122 is depressed by the cassette casing to be turned on as shown in FIG. 5A. Then, it is identified that the cassette is the existing cassette, and also, an existing erroneous erasure prevention detecting switch 131 is turned on by an erroneous erasure prevention member 133 to become a recordable state.
Further, when the erroneous erasure prevention member 133 is moved to make the existing erroneous erasure prevention hole 107 become the open state, the existing erroneous erasure prevention detecting switch 131 is turned off to become a non-recordable state as shown in FIG. 5B.
However, since a reduction in size and in weight with respect to, for example, a recording and reproducing apparatus such as the VTR has been advancing year by year, there has been a problem in which when the above described two detecting switches are to be added, a space for new detecting switches may not be secured in the drive unit of an existing recording and reproducing apparatus and it is not possible to use an existing drive unit.